Back to EveryPatent.com
| United States Patent |
5,635,324
|
|
Rasmussen
, et al.
|
June 3, 1997
|
Multilayered photoreceptor using a roughened substrate and method for
fabricating same
Abstract
A photoreceptor and method eliminate interference-fringe print defect due
to interference effects caused by reflected beams from various interfaces
in a multilayered photoreceptor. The substrate surface is formed with
specific dimensions so as to enable the coating of the substrate with an
undercoat film including, for example, an organometallic compound or an
organometallic chelate compound such as any suitable hydrolyzable
organozirconium, organotitanium or organoaluminum compound with a silane.
Elimination of the "pepper spot" print defect is accomplished without the
addition of a thickening agent to the undercoat film.
| Inventors:
|
Rasmussen; Yonn K. (Fairport, NY);
Foley; Geoffrey M. T. (Fairport, NY);
Post; Richard L. (Penfield, NY);
Yu; Robert C. U. (Webster, NY);
Mishra; Satchidanand (Webster, NY);
Yanus; John F. (Webster, NY)
|
| Assignee:
|
Xerox Corporation (Stamford, CT)
|
| Appl. No.:
|
407469 |
| Filed:
|
March 20, 1995 |
| Current U.S. Class: |
430/58.8; 430/58.75; 430/60; 430/64; 430/127; 430/131 |
| Intern'l Class: |
G03G 005/047; G03G 005/14 |
| Field of Search: |
430/60,62,64,127,131,58
|
References Cited
U.S. Patent Documents
| 4076564 | Feb., 1978 | Fisher | 156/664.
|
| 4134763 | Jan., 1979 | Fujimura et al. | 427/299.
|
| 4390611 | Jun., 1983 | Ishikawa et al. | 430/59.
|
| 4551404 | Nov., 1985 | Hiro et al. | 430/59.
|
| 4588667 | May., 1986 | Jones et al. | 430/73.
|
| 4596754 | Jun., 1986 | Tsutsui et al. | 430/58.
|
| 4618552 | Oct., 1986 | Tanaka et al. | 430/60.
|
| 4741918 | May., 1988 | Nagy de Nagybaczon et al. | 427/180.
|
| 4797337 | Jan., 1989 | Law et al. | 430/58.
|
| 4904557 | Feb., 1990 | Kubo | 430/56.
|
| 4965155 | Oct., 1990 | Nishiguchi et al. | 430/58.
|
| 5004662 | Apr., 1991 | Mutoh et al. | 430/59.
|
| 5051328 | Sep., 1991 | Andrews et al. | 430/56.
|
| 5069758 | Dec., 1991 | Herbert et al. | 205/73.
|
| 5089908 | Feb., 1992 | Jodoin et al. | 359/212.
|
| 5096792 | Mar., 1992 | Simpson et al. | 430/58.
|
| 5188916 | Feb., 1993 | Hodumi et al. | 430/65.
|
| 5252422 | Oct., 1993 | Okano et al. | 430/131.
|
| 5286591 | Feb., 1994 | Hongo | 430/60.
|
| 5399452 | Mar., 1995 | Takegawa et al. | 430/56.
|
| 5464717 | Nov., 1995 | Sakaguchi et al. | 430/58.
|
Primary Examiner: Martin; Roland
Attorney, Agent or Firm: Oliff & Berridge
Claims
What is claimed is:
1. A method of making a photoreceptor having a multilayered structure
including a substrate and an undercoat film covering said substrate, said
method comprising the steps of:
forming peaks and valleys in the substrate to have a core roughness depth
(R.sub.k) of about 0.1-0.7 .mu.m, an arithmetic mean of the five highest
of said peaks and the five deepest of said valleys (R.sub.ZISO) of about
0.1-1.2 .mu.m, an arithmetic average slope of all profile peaks (D.sub.a)
of below about 0.08 .mu.m and an arithmetic mean value (R.sub.a) of the
amplitudes of all peaks and valleys ranging between about 0.05-0.5 .mu.m;
forming no fewer than about 200 of said peaks and valleys over a 10 mm
length with a peak to valley distance of at least about 0.2 .mu.m;
coating the substrate with said undercoat film;
forming a charge generating layer over said undercoat film; and
forming a charge transport layer over said charge generating layer,
wherein said multilayered photoreceptor is suitable for use in xerographic
printers capable of producing print output substantially free of pepper
spots, and interference-fringe defect that would otherwise be produced due
to specular reflection along an interface between the substrate and the
undercoat film.
2. The method according to claim 1, wherein said forming step includes
forming said peaks and valleys to have a maximum roughness value (Rmax) of
no greater than about 1.5 .mu.m.
3. The method according to claim 1, wherein said forming step includes
forming said peaks and valleys to have a maximum roughness value (Rmax) of
no greater than about 1.0 .mu.m.
4. The method according to claim 1, wherein said core roughness depth
(R.sub.k) is about 0.2-0.5 .mu.m, said arithmetic mean of the five highest
and five lowest of said peaks and valleys (R.sub.ZISO) is about 0.5-0.8
.mu.m, the arithmetic average slope (D.sub.a) is less than about 0.06
.mu.m, and the arithmetic mean value (R.sub.a) is about 0.05-0.02 .mu.m.
5. The method according to claim 1, wherein said forming step and said
coating step further comprise eliminating specular reflections of an
incident light beam from an interface between said undercoat film and said
substrate.
6. The method according to claim 1, wherein said forming step includes
diamond lathing the substrate.
7. The method according to claim 1, wherein said coating step includes
coating said undercoat film on said substrate with a thickness of
approximately 0.05-0.5 .mu.m.
8. The method according to claim 7, wherein said undercoat film has a
thickness between 0.08-0.12 .mu.m.
9. The method according to claim 1, wherein said undercoat film comprises
one of an organometallic compound and an organometallic chelate compound
with a silane.
10. The method according to claim 9, wherein said undercoat film comprises
an undercoat film substantially without a thickening agent.
11. The method according to claim 10, wherein said undercoat film comprises
acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane.
12. The method according to claim 10, wherein said undercoat film comprises
a silane and one of an organozirconate compound, an organozirconate
chelate compound, an organotitanate compound, an organotitanate chelate
compound, an organoaluminate compound and an organoaluminate chelate
compound.
13. The method according to claim 10, wherein said silane comprises a
hydrolyzable organo silane represented by the following formula:
##STR2##
wherein R1 is an alkylidene group containing 1 to 20 carbon atoms, R2 and
R3 are independently selected from the group consisting of H, a lower
alkyl group containing 1 to 3 carbon atoms, a phenyl group and a
poly(ethyleneamino) group, and R4, R5, and R6 are independently selected
from a lower alkyl group containing 1 to 4 carbon atoms.
14. The method according to claim 9, wherein said undercoat film comprises
a silane and one of an organozirconate compound, an organozirconate
chelate compound, an organotitanate compound, an organotitanate chelate
compound, an organoaluminate compound and an organoaluminate chelate
compound.
15. The method according to claim 9, wherein said silane comprises a
hydrolyzable organo silane represented by the following formula:
##STR3##
wherein R1 is an alkylidene group containing 1 to 20 carbon atoms, R2 and
R3 are independently selected from the group consisting of H, a lower
alkyl group containing 1 to 3 carbon atoms, a phenyl group and a
poly(ethyleneamino) group, and R4, R5, and R6 are independently selected
from a lower alkyl group containing 1 to 4 carbon atoms.
16. The method according to claim 1, wherein said undercoat film comprises
an undercoat film substantially without a thickening agent.
17. A multilayered photoreceptor comprising:
a roughened substrate having no fewer than about 200 peaks and valleys over
a 10 mm length with a peak to valley distance of at least about 0.2 .mu.m;
an undercoat film formed on said substrate, said undercoat film comprising
a mixture of a silane and one of an organometallic compound and an
organometallic chelate compound, said undercoat film being substantially
without a thickening agent;
a charge generating layer formed over the undercoat film; and
a charge transport layer overlaying said charge generating layer,
wherein said multilayered photoreceptor is suitable for use in xerographic
printers capable of producing print output substantially free of pepper
spots and interference-fringe defect that would otherwise be produced due
to specular reflection along an interface between the substrate and the
undercoat film.
18. The photoreceptor according to claim 17, wherein said undercoat film
comprises a silane and one selected from the group consisting of an
organozirconate compound, an organozirconate chelate compound, an
organotitanate compound, an organotitanate chelate compound, an
organoaluminate compound and an organoaluminate chelate compound.
19. The photoreceptor according to claim 17, wherein said undercoat film
comprises acetylacetone zirconium tributoxide and
aminopropyltrimethoxysilane.
20. The photoreceptor according to claim 17, wherein said silane comprises
a hydrolyzable organo silane represented by the following formula:
##STR4##
where R1 is an alkylidene group containing 1 to 20 carbon atoms, R2 and R3
are independently selected from the group consisting of H, a lower alkyl
group containing 1 to 3 carbon atoms, a phenyl group and a
poly(ethyleneamino) group, and R4, R5, and R6 are independently selected
from a lower alkyl group containing 1 to 4 carbon atoms.
21. The photoreceptor according to claim 17, wherein said peaks and valleys
have a core roughness depth (R.sub.k) of about 0.1-0.7 .mu.m, an
arithmetic mean of the five highest of said peaks and the five deepest of
said valleys (R.sub.ZISO) of about 0.1-1.2 .mu.m, an arithmetic average
slope (D.sub.a) is less than about 0.08 .mu.m, and an arithmetic mean
value of the amplitudes of all said peaks and said valleys (R.sub.a)
between about 0.05-0.5 .mu.m.
22. The photoreceptor according to claim 21, wherein said peaks and valleys
have a maximum roughness value (Rmax) of no greater than about 1.5 .mu.m.
23. The photoreceptor according to claim 21, wherein said peaks and valleys
have a maximum roughness value (Rmax) of no greater than about 1.0 .mu.m.
24. The photoreceptor according to claim 21, wherein said core roughness
depth (R.sub.k) is about 0.2-0.5 .mu.m, said arithmetic mean of the five
highest and five lowest of said peaks and valleys (R.sub.ZISO) is about
0.5-0.8 .mu.m, the arithmetic average slope (D.sub.a) is less than about
0.06 .mu.m, and the arithmetic mean R.sub.a is about 0.05-0.2 .mu.m.
25. The photoreceptor of claim 17, wherein said charge generating layer
comprises oxytitanium phthalocyanine IV and chloroindium phthalocyanine in
a polyvinyl butyral resin binder, and said charge transport layer
comprises tri-p-tolylamine and
N,N'-diphenyl-N,N'-bis-1,1'-biphenyl-4,4'-diamine in a polycarbonate resin
binder.
26. The photoreceptor according to claim 17, further comprising a
single-layer photosensitive layer comprising said charge generating layer
and said charge transporting layer.
27. The photoreceptor according to claim 17, wherein said undercoat film
has a thickness of about 0.05-0.5 .mu.m.
28. The photoreceptor according to claim 27, wherein said undercoat layer
thickness is about 0.08-0.12 .mu.m.
29. A method of eliminating pepper spots from print output and specular
reflection from an interface between a substrate and an undercoat film of
a photoreceptor, said method comprising the steps of:
forming said substrate to have a roughness enabling said substrate to be
coated with said undercoat film substantially without a thickening agent,
said substrate having no fewer than about 200 peaks and valleys over a 10
mm length with a peak to valley distance of at least about 0.2 .mu.m;
coating said substrate with said undercoat film; and
forming charge generating and transport layers overlaying the undercoat
film,
wherein said multilayered photoreceptor is suitable for use in xerographic
printers capable of producing print output substantially free of
interference-fringe defect and pepper spots.
30. The method according to claim 29, wherein said forming step further
comprises:
diamond lathing the peaks and valleys;
dimensioning the peaks and valleys so that a core roughness depth (R.sub.k)
is about 0.1-0.7 .mu.m, an arithmetic mean value of the five highest of
said peaks and the five lowest of said valleys (R.sub.ZISO) is between
about 0.1-1.2 .mu.m, an arithmetic average shape (D.sub.a) of all the
profile peaks is less than about 0.08 .mu.m, and an arithmetic mean value
of the amplitudes of all of the peaks and valleys (R.sub.a) is about
0.05-0.5 .mu.m.
31. The method according to claim 30, wherein said peaks and valleys to
have a maximum roughness value (Rmax) of no greater than about 1.5 .mu.m.
32. The method according to claim 30, wherein said peaks and valleys to
have a maximum roughness value (Rmax) of no greater than about 1.0 .mu.m.
33. The method according to claim 30, wherein said core roughness depth
(R.sub.k) is about 0.2-0.5 .mu.m, said arithmetic mean of the five highest
and five lowest of said peaks and valleys (R.sub.ZISO) is about 0.5-0.8
.mu.m, the arithmetic average slope (D.sub.a) is less than about 0.06
.mu.m, and the arithmetic mean value (R.sub.a) is about 0.05-0.2 .mu.m.
34. The method according to claim 29, wherein said undercoat film comprises
one of an organometallic compound and an organometallic chelate compound
with a silane, and said coating step comprises coating said substrate with
one of said organometallic compound and said organometallic chelate
compound with a silane.
35. The method according to claim 34, wherein said coating step comprises
coating said substrate with said undercoat film having a thickness of
about 0.05-0.5 .mu.m.
36. The method according to claim 35, wherein said undercoat film thickness
is about 0.08-0.12 .mu.m.
37. The method according to claim 29, wherein said coating step comprises
coating said undercoat film on a non-liquid honed substrate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to photoreceptors suitable for application to
xerographic printers and like machines that use coherent light sources and
methods for fabricating photoreceptors. More particularly, this invention
relates to a multilayered photoreceptor having a conductive substrate
having a designated surface roughness that eliminates an
interference-fringe print defect in the resulting printer output and
enables the use of undercoat layer materials, such as an organometallic or
organometallic chelate compound with a silane, examples of which include
any suitable hydrolyzable organozirconium, organotitanium or
organoaluminum compound with a silane. The invention also relates to a
fabrication method for forming a substrate, for example a metallic
substrate, of a multilayered photoreceptor to produce a specific surface
morphology and surface roughness, and coating the roughened substrate with
the undercoat film without a thickening agent.
2. Description of Related Art
Xerographic printers and like machines that use multilayered photoreceptors
in conjunction with a coherent light source suffer from an interference
effect that manifests as a printable defect that can be described as a
series of dark and light interference fringes that resemble wood grains.
The use of coherent illumination sources in conjunction with multilayered
photoreceptors produces the interference effect through the interaction
between various reflected components of the incident light whose
difference in optical path length varies from one area of the
photoreceptor to another. Such spatial variation in the optical path
length arises because the coated layers have inherent spatial thickness
variations imposed by limitations in the coating process. The spatial
variation in the optical path length in turn produces absorption variation
in the charge generating layer of the photoreceptor, resulting in the
interference-fringe defect in prints generated by these xerographic
machines.
FIG. 1 is a schematic view of a typical photoreceptor of a multilayered
design. In FIG. 1, the photoreceptor 10 includes a substrate 1, an
undercoat layer 2, a charge generating layer 3, and a charge transport
layer 4.
In the present device, which comprises three organic layers 2-4 coated on a
metallic substrate 1, an incident light beam 5 is directed at the charge
transport layer 4. The primary light beam 5 is then reflected from the
planes that define interfaces 7, 9A, 9B and 9C between the layers 1-4 of
the multilayered photoreceptor. More specifically, reflected light beam 6
is generated via reflection from the interface 7 between the atmospheric
air and the charge transport layer 4, reflected light beam 8A is generated
via reflection from the interface 9A between the charge transport layer 4
and the charge generating layer 3, reflected light beam 8B is generated
via reflection from the interface 9B between the charge generating layer 3
and the undercoat layer 2, and reflected light beam 8C is generated via
reflection from the interface 9C between the undercoat layer 2 and the
substrate 1. The primary reflections that contribute to the
interference-fringe print defect producing interference effect are the
reflected beam 6 generated at the interface 7 between the surrounding
atmospheric air and the charge transport layer 4 and the reflected beam 8C
from the interface 9C between the undercoat layer 2 and the substrate 1,
where the differences in optical indices are the greatest.
Many methods have been proposed to suppress the charge transport layer/air
interface specular reflection, including roughening of the charge
transport layer surface by introducing SiO.sub.2 and other particles into
the charge transport layer, applying an appropriate overcoating layer and
the like.
Many methods have also been proposed to suppress the intensity of substrate
surface specular reflection, e.g., coating specific materials such as
anti-reflection materials and light scattering materials on the substrate
surface and roughening methods such as anodization, dry blasting and
liquid honing of the substrate surface. However, such methods must achieve
their primary objective of eliminating substrate surface reflections
without adversely impacting the electrical parameters or print quality of
photoreceptors into which they are incorporated.
Patents on interference-fringe effect suppression in general and
suppression of the substrate surface reflection in particular include
Tanaka et al. U.S. Pat. No. 4,618,552 (adding an opaque conductive layer
above the ground plane), Nagy de Nagybaczon et al. U.S. Pat. No. 4,741,918
(coating process using a buffing wheel), Kubo et al. U.S. Pat. No.
4,904,557 (roughened photosensitive layer on top of a smooth substrate
surface), Fujimura et al. U.S. Pat. No. 4,134,763 (grinding method to
roughen the substrate surface), Simpson et al. U.S. Pat. No. 5,096,792
(addition of antireflection layer on top of the substrate surface), and
Andrews et al. U.S. Pat. No. 5,051,328 (Indium Tin Oxide transparent
ground plane as the substrate).
A liquid honing process, for example, is an effective technique to create a
highly scattered surface on a metallic substrate, and is used in some
multilayered devices to eliminate the interference-fringe effect. The
method, however, has several disadvantages which the present invention
overcomes.
For example, the liquid honing process is an added step following diamond
lathing which thereby increases the cost of production of a substrate. The
surface morphology of the substrate created by liquid honing method also
does not lend itself to be used in conjunction with a thin-film forming
undercoat layer material, such as the aforementioned organometallic or
organometallic chelate compound with a silane, due to the nature of the
surface texture that is undesirable for a thin-layer coating in the
thickness range of approximately 0.05-0.5 .mu.m and still provides
complete surface coverage of the substrate. It is required that the
thin-film forming undercoat layer materials provide continuous coverage of
the underlying metallic substrate in order that print defects due to
charge injection from the substrate are eliminated.
In typical multilayered photoreceptors, a resins layer is inserted as an
undercoat layer between the substrate and the photosensitive layers in
order to provide mechanical strength, better adhesion between the
substrate and the photosensitive layers and improved cyclic stability.
Each intermediate layer may be any layer conventionally employed between
the substrate and the photosensitive layer as illustrated for example in
Tanaka et al., U.S. Pat. No. 4,618,552 and Andrews et al., U.S. Pat. No.
5,051,328, the disclosures of which are incorporated herein by reference.
Accordingly, the intermediate layer may be a subbing layer, barrier layer,
adhesive layer, and the like. The intermediate layer may be formed of, for
example, casein, polyvinyl alcohol, nitrocellulose, ethyleneacrylic acid
copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon,
alkoxymethylated nylon, and the like), polyurethane, gelatin, and the
like. Intermediate adhesive layers between the substrate and the
subsequently applied layers may be desirable to improve adhesion. Typical
adhesive layers include film-forming polymers such as polyester,
polyvinylbutyral, polyvinylpyrrolidone, polycarbonate, polyurethane,
polymethyl methacrylate, and the like as well as mixtures thereof. The
intermediate layer may be deposited by any conventional means such as dip
coating and vapor deposition and preferably has a thickness of from about
0.05 to about 5 microns.
Typical resin layers, however, exhibit poor environmental cyclic stability
due to the fact that the volume resistivity of a resin greatly depends on
the ionic conductivity and is strongly affected by temperature and
humidity conditions. Many proposals have been made to form an undercoat
layer using organic metal compounds or silane coupling agents to improve
upon the environmental effects. Okano et al. U.S. Pat. No. 5,252,422 and
Hodumi et al. U.S. Pat. No. 5,188,916, for example, discuss the use of
organic metal chelate compounds or organic metal alkoxide compounds with
silane coupling agents as an improved undercoat layer in a multilayered
photoreceptor for visible light xerographic applications. When this type
of an undercoat material is used in combination with a roughened substrate
for interference fringe suppression for printer applications where a
coherent exposure light source is used, an addition of a resin is required
to increase the thickness of the undercoat layer to ensure continuous
coverage to avoid charge injection from the substrate. Examples of a print
defect caused by charge injection from the substrate include a cluster of
black spots in a white background in a discharge area development (DAD)
system, which are commonly known as "pepper spots."
Thick undercoat layers, however, produce undesirable electrical effects
including a high residual voltage build up and poor cyclic stability. An
example of a thick undercoat layer including an organometallic or an
organometallic chelate compound is a mixture of acetylacetone zirconium
tributoxide and .gamma.-aminopropyltrimethoxysilane and solvents and a
polyvinyl butyral resin added as a thickening agent. In order to suppress
residual build up in a low temperature and low humidity condition in
particular, fabrication using this type of a mixture containing a resin
requires a humidification step that results in increased unit
manufacturing costs and decreased throughput efficiency. Hongo et al. U.S.
Pat. No. 5,286,591 also discloses a subbing layer containing an organic
chelate compound or an organic alkoxide compound but with a hygroscopic
compound having at least two carboxyl groups per molecule to improve upon
environmental cyclic stability. A resin binder is also used to increase
the thickness of the subbing layer in the case where interference-fringe
image defect suppression is required via roughening of a substrate using a
liquid honing method.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the shortfalls from
conventional techniques by providing a method of suppressing or
eliminating the strong specular reflection from an undercoat/substrate
interface to eliminate the printable interference-fringe defect in
xerographic printers and like machines that use coherent illumination as
the exposure light source.
Another object of the present invention is to provide a method for making a
photoreceptor using a forming method, for example, a diamond lathing
process, that produces specific surface roughness on the conductive
substrate, whereby a thin-film forming undercoat layer material, such as a
mixture of any suitable hydrolyzable organozirconium, organotitanium or
organoaluminum compound and a silane in appropriate solvents, can be
directly applied to a roughened substrate such as a diamond lathed
substrate, at a desired coating thickness without any addition of a resin
as a viscosity increasing agent. Examples of organometallic and
organometallic chelate compounds include organotitanate and organotitanate
chelate compounds, organozirconate and organozirconate chelate compounds
and organoaluminate and organoaluminate chelate compounds.
Examples of hydrolyzable organo silane may be reperesented by the following
formula:
##STR1##
wherein R1 is an alkylidene group containing 1 to 20 carbon atoms, R2 and
R3 are independently selected from the group consisting of H, a lower
alkyl group containing 1 to 3 carbon atoms, a phenyl group and a
poly(ethyleneamino) group, and R4, R5, and R6 are independently selected
from a lower alkyl group containing 1 to 4 carbon atoms. The
organoaminosilane is hydrolyzed in an aqueous solution with the
organometallic compound. Typical hydrolyzable silanes include
.gamma.-aminopropyl triethoxy silane, (N,N-dimethyl 3-amino) propyl
triethoxysilane, N,N-dimethylaminophenyl silane, N-phenyl aminopropyl
trimethoxy silane, triethoxy silylpropylethylene diamine, trimethoxy
silylpropylethylene diamine, trimethoxy silylpropyldiethylene triamine,
N-aminoethyl-3-aminopropyltrimethoxysilane,
N-2-aminoethyl-3-aminopropyltrimethoxysilane,
N-2-aminoethyl-3-aminopropyltris(ethylethoxy)silane, p-aminophenyl
trimethoxysilane, 3-aminopropyldiethylmethylsilane, N,N'-dimethyl
3-amino)propyltriethoxysilane, 3-aminopropylmethyldiethoxysilane,
.gamma.-aminopropyl trimethoxysilane, N-methylaminopropyltriethoxysilane,
methyl[2-(3-trimethoxysilylpropylamino)ethylamino]-3-proprionate,
(N,N'-dimethyl 3-amino)propyl triethoxysilane,
N,N-dimethylaminophenyltriethoxy silane,
trimethoxysilylpropyldiethylenetriamine and mixtures thereof.
A further object of the present invention is to provide a multilayered
photoreceptor including a diamond lathed substrate that does not require
liquid honing after diamond lathing, and to provide a thin-film undercoat
layer overlaying the substrate, wherein the undercoat layer has the coated
thickness in the range of 0.05 to 0.5 micron. An example of such a
thin-film forming undercoat layer material includes an organometallic or
organometallic chelate compound with a silane such as a mixture of
acetylacetone zirconium tributoxide and
.gamma.-aminopropyl-trimethoxysilane without the addition of a polyvinyl
butyral resin as a thickening agent.
In accordance with a first aspect of the present invention, there is
provided a method of making a photoreceptor having a substrate and an
undercoat film. The method includes forming the substrate with a specified
core roughness with respect to the dimensions of the peaks and valleys of
the substrate, and coating the substrate with the undercoat film. The
thickness of the undercoat film may be in the range of 0.05-0.5 micron.
The forming step may be a diamond lathing step, and the undercoat film,
such as an organometallic or an organometallic chelate compound with a
silane layer, may have a thickness of 0.05-0.5 .mu.m, that provides
continuous coverage of the substrate, thereby avoiding "pepper spots."
In accordance with a second aspect of the present invention, there is
provided a multilayered photoreceptor having a roughened substrate and an
undercoat film comprising a silane and an organometallic or an
organometallic chelate compound. The undercoat film is substantially
without a thickening agent and does not require a thickening agent or a
humidification step for processing. The undercoat film may comprise a
mixture of an acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane, i.e., one that does not require a
polyvinyl butyral resin as a thickening agent or a humdification
processing step.
With this arrangement, it is possible to produce a multilayered organic
photoreceptor that does not require liquid honing of the substrate after
diamond lathing, adding a thickening agent to the undercoat layer to
ensure continuous coverage of the undercoat layer, or using a
humidification step in manufacturing.
According to a third aspect of the invention, there is provided a method of
eliminating specular reflection from an interface between a substrate and
an undercoat film comprising the steps of forming the substrate to have a
roughness that enables the substrate to be coated with the undercoat film
substantially without a thickening agent, and coating the substrate with
the undercoat film.
These and other aspects and advantages of the present invention are
described in or apparent from the following detailed description of
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in detail with reference to the following
drawings, wherein:
FIG. 1 is a schematic cross-sectional view showing the primary reflections
that contribute to the interference effect in a multilayered conventional
device;
FIG. 2 is a schematic cross-sectional view of the photoreceptor of the
present invention; and
FIG. 3 illustrates the Material Ratio Curve or Abbott-Firestone curve.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention will now be described in detail by way of preferred
embodiments of the manufacturing method referred to in the drawings. The
present invention is applicable to any fabrication process involving
forming, for example, by diamond lathing, a conductive substrate and
coating the substrate with a thin-film forming undercoat layer such as a
any suitable hydrolyzable organozirconium, organotitanium or
organoaluminum compound with a silane, for example, a mixture of
acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane in appropriate solvents. The desired
dried coated thickness for the undercoat layer ranges between 0.05-0.5
micron and preferably between 0.08-0.12 micron. The present invention is
particularly desirable for use in conjunction with organic multilayered
photoreceptors used with a coherent light source to suppress interference
fringes. The unit manufacturing costs of these photoreceptors can be
reduced because there is no need for a liquid honing step after diamond
lathing of the substrate in cases where a liquid honing is currently used,
the addition of a thickening agent such as a polyvinyl butyral resin to
the undercoat layer, or a humidification step during manufacturing.
FIG. 2 is a schematic cross sectional view of the photoreceptor of the
present invention. A multilayered photoreceptor 20 includes a substrate
11, an undercoat film or layer 12 overlaying the substrate, a charge
generating layer 13 overlaying the undercoat film, and a charge transport
layer 14 overlaying the charge generating layer 13.
The conductive substrate is typically aluminum and generally cylindrical,
and is cleaned by any suitable technique after the surface morphology of
the substrate is formed. Other types of conductive materials including
conductive plastic and other metals and metal alloys such as stainless
steel, brass and the like can be also employed as a substrate. If diamond
lathing is used to create the surface roughness, the lathing lubricants
and any foreign substances introduced to the substrate surface during
diamond lathing are removed. Although FIG. 2 is intended to portray a
cross-sectional view of cylindrical substrate, any substrate geometry such
as a hollow or solid cylinder, a flat sheet, a seamed or unseamed belt, or
any other form that allows conventional coating techniques such as dip
coating, vapor deposition and the like can be used. The substrate may be
finished with one or more undercoat layers and/or a photosensitive layer
as follows.
One or more of any suitable hydrolyzable organozirconium, organotitanium or
organoaluminum compound with a silane as an undercoat film 12 may be
employed in embodiments of the present invention. Examples of
aforementioned organometallic and organometallic chelate compounds include
organotitanate and organotitanate chelate compounds, organozirconate and
organozirconate chelate compounds and organaluminate and organoaluminate
chelate compounds. Specific examples include acetyl acetonate titanate
chelate, ethyl acetoacetate titanate chelate, triethanolamine titanate
chelate, lactic acid titanate chelate, neopentyl(diallyl)oxy,
tri(N-ethylenediamino) ethyl titanate, neopentyl(diallyl)oxy,
tri(m-amino)phenyl titanate, cyclo(dioctyl)pyrophosphato dioctyl titanate,
cyclo(dioctyl)pyrophosphato dioctyl zirconate, and diisobutyl (oleyl)
aceto acetyl aluminate and diisopropyl (oleyl) aceto acetyl aluminate.
Typical hydrolyzable silanes include .gamma.-aminopropyl triethoxy silane,
(N,N-dimethyl 3-amino) propyl triethoxysilane, N,N-dimethylaminophenyl
silane, N-phenyl aminopropyl trimethoxy silane, triethoxy,
silylpropylethylene diamine, trimethoxy silylpropylethylene diamine,
trimethoxy silylpropyldiethylene triamine,
N-aminoethyl-3-aminopropyltrimethoxysilane,
N-2-aminoethyl-3-aminopropyltrimethoxysilane,
N-2-aminoethyl-3-aminopropyltris(ethylethoxy)silane, p-aminophenyl
trimethoxysilane, 3-aminopropyldiethylmethylsilane, (N,N'-dimethyl
3-amino)propyltriethoxysilane, 3-aminopropylmethyldiethoxysilane,
.gamma.-aminopropyl trimethoxysilane, N-methylaminopropyltriethoxysilane,
methyl[2-(3-trimethoxysilylpropylamino)-ethylamino]-3-proprionate,
(N,N'-dimethyl 3-amino)propyl triethoxysilane,
N,N-dimethylaminophenyltriethoxy silane,
trimethoxysilylpropyldiethylenetriamine and mixtures thereof. The
preferred silane materials are .gamma.-aminopropyltriethoxysilane,
.gamma.-aminopropyltrimethoxysilane,
N-aminoethyl-3-aminopropyltrimethoxysilane, (N,N'-dimethyl
3-amino)propyltriethoxysilane, and the like or mixtures thereof because
the hydrolyzed solutions of these materials exhibit a greater degree of
basicity and stability and because these materials are readily available
commercially.
In embodiments, a charge transport layer 14 and a charge generating layer
13 comprise the photosensitive layers. This is referred to as a laminate
type photosensitive material. Charge transport and charge generating
layers may be deposited by any suitable conventional technique including
dip coating and vapor deposition and are well known in the art as
illustrated for example in U.S. Pat. No. 4,390,611, U.S. Pat. No.
4,551,404, U.S. Pat. No. 4,588,667, U.S. Pat. No. 4,596,754, and U.S. Pat.
No. 4,797,337, the disclosures of which are incorporated herein by
reference. In embodiments, the charge generating layer 13 may be formed by
dispersing a charge generating material selected from commercially
available azo pigments such as Sudan Red, Dian Blue, Janus Green B, and
the like; quinone pigments such as Algol Yellow, Pyrene Quinone,
Indanthrene Brilliant Violet RRP, and the like; quinocyanine pigments;
perylene pigments; indigo pigments such as indigo, thioindigo, and the
like; bisbenzoimidazole pigments such as Indofast Orange toner, and the
like; phthalocyanine pigments such as copper phthalocyanine,
aluminochloro-phthalocyanine, oxytitanium phthalocyanine, chloroindium
phthalocyanine and the like; quinacridone pigments; or azulene compounds
in a binder resin such as polyester, polystyrene, polyvinyl butyral,
polyvinyl pyrrolidone, methyl cellulose, polyacrylates, cellulose esters,
and the like. In embodiments, the charge transport layer may be formed by
dissolving a positive hole transporting material selected from compounds
having in the main chain or the side chain a polycyclic aromatic ring such
as anthracene, pyrene, phenanthrene, coronene, and the like, or a
nitrogen-containing hetero ring such as indole, carbazole, oxazole,
isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline,
thiadiazole, triazole, and the like, and hydrazone compounds in a resin
having a film-forming property. Such resins may include polycarbonate,
polymethacrylates, polyarylate, polystyrene, polyester, polysulfone,
styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer,
and the like.
In embodiments, the photosensitive material may be of a single-layer type
comprising the charge generating material, charge transporting material,
and the binder resin, wherein these three materials may be as described
above. Single layer type photosensitive materials may be deposited by an
suitable technique including dip coating and vapor deposition and are
illustrated, for example, in Mutoh et al., U.S. Pat. No. 5,004,662 and
Nishiguchi et al., U.S. Pat. No. 4,965,155, the disclosures of which are
incorporated herein by reference.
In operation, an incident light beam 15 is reflected from various layers of
the multilayered photoreceptor. In particular, a reflected beam 16 is
generated from the interface 19 between the charge transport layer 14 and
the atmospheric air surrounding the photoreceptor, a beam 17 is generated
from the interface 21 between the charge generating layer 13 and the
charge transport layer 14, and a beam 18 is produced by the interface 22
between the charge generating layer 13 and the undercoat layer 12.
As compared with FIG. 1, the photoreceptor of FIG. 2 does not generate a
strong specular reflection from the interface 23 between the substrate and
the undercoat layer. The interference effect can be minimized or
eliminated if the strong specular reflection from the charge transport
layer surface or the strong specular reflection from the substrate surface
is eliminated or suppressed. By creating a substrate surface with the
desired surface characteristics, the intensity of the primary specular
reflection is suppressed. The method by which the undercoat
layer/substrate specular reflection is minimized or eliminated will now be
described.
According to the method for eliminating interference between the substrate
and the undercoat layer interface, the substrate 11 is formed to include a
surface texture that is optimal for enabling continuous coating of
thin-film forming undercoat layer materials such as any of the
aforementioned suitable organometallic or organometallic chelate compounds
with a silane having a dried coated thickness between approximately
0.05-0.5 .mu.m and preferably between 0.08-0.12 .mu.m. In order for the
substrate to accommodate a thin layer of such undercoat materials, the
substrate of the photoreceptor is designed to have a specified roughness.
Specifically, the surface texture of the substrate is described by a set of
parameters: the core roughness depth R.sub.k, found in the
Abbott-Firestone curve or the Material Ratio Curve; the mean roughness
R.sub.a ; the average distance of the five highest peaks to the five
lowest valleys in a given sampling length, R.sub.ZISO ; the maximum
roughness depth, R.sub.max ; the average slope D.sub.a and Peak Count
R.sub.t1(0.1). Each of these parameters is described in detail below.
FIG. 3 illustrates the Material Ratio Curve, which is the graphical
representation of material ratio calculated throughout the depth of the
profile. R.sub.k is the depth of the core roughness profile for which the
Material Ratio Curve can be closely approximated by a bestfit straight
line which is determined by a secant to the Material Ratio Curve
representing the smallest rise over a material ratio range of 40%. R.sub.a
is the arithmetic average of all departures of the roughness profile from
the center line within the evaluation length. R.sub.a is defined by a
formula:
##EQU1##
in which l.sub.m represents the evaluation length, .vertline.y.vertline.
represents the absolute value of departures of the roughness profile from
the center line.
The expression R.sub.max represents the largest single roughness gap within
the evaluation length. The evaluation length is that part of the
traversing length that is evaluated. An evaluation length containing five
consecutive sampling lengths is taken as a standard. R.sub.ZISO can also
be defined by a formula:
##EQU2##
in which Y.sub.pi represents the value of departure of the roughness
profile above the center line from the center line, and Y.sub.vi
represents the value of departure of the roughness profile below the
center line from the center line. D.sub.a is the arithmetic average slope
of all profile peaks within the evaluation length l.sub.m. Peak count
Rt(x) is defined as the number of peaks which have risen above the upper
reference level and have fallen adjacently below the lower reference
level. Peak count is always related to a length of 10 mm. The reference
level is determined by the value of x and the upper and lower reference
levels are symmetrical to the center line. The reference level is
therefore 0.1 micron for R.sub.t1 (0.1).
These measurements may be made with a profilameter such as Model S8P
manufactured by Mahr Feinpruef Corporation. Generally, a stylus with a
diamond tip is traversed over the surface of the roughened substrate at a
constant speed to obtain all data points within an evaluation length. The
radius of curvature of the diamond tip used to obtain all data referred to
herein is 5 microns.
For the present embodiment, R.sub.k is in the range of about 0.1-0.7 .mu.m
and preferably between 0.2-0.5 .mu.m, R.sub.ZISO is in the range of about
0.1-1.2 .mu.m and preferably between 0.5-0.8 .mu.m, R.sub.a is in the
range of about 0.05-0.5 .mu.m and preferably between 0.05-0.2 .mu.m,
R.sub.max is below about 1.5 .mu.m and preferably below 1 .mu.m, D.sub.a
is below about 0.08 .mu.m and preferably below 0.06 .mu.m, and
R.sub.t1(0.1) is greater than about 100 counts and preferably greater than
about 200 counts.
With a photoreceptor having a substrate roughened within the above
specified ranges for the different roughness parameters mentioned above,
it is possible to coat a continuous layer of thin-film forming undercoat
layer materials that include any suitable hydrolyzable organozirconium,
organotitanium or organoaluminum compound with a silane. An example of
such an undercoat materials includes a mixture of acetylacetone zirconium
tributoxide and .gamma.-aminopropyltrimethoxysilane and solvents, without
adding a polyvinyl butyral resin as a thickening agent to increase its
viscosity from approximately 3-5 centipoise to above 10 centipoise and
without humidification treatment after coating. This enables a thin-film
coating in the range 0.05-0.5 micron, provides continuous coverage of the
undercoat layer on the substrate and eliminates or suppresses interference
fringes to an acceptable level and does not require separate liquid honing
of the substrate after diamond lathing if diamond lathing is used for
roughening the substrate surface.
The use of acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane and solvents in combination with a
roughened substrate without a thickening agent, rather than the same
solution formulation with a thickening agent such as a polyvinyl butyral
resin as a viscosity increasing agent, provides two advantages. First, it
provides commonality for the undercoat layer solution between other
multilayered photoreceptors designed for printer applications with a
coherent exposure light source and like machines using roughened
substrates for interference-fringe defect suppression and photoreceptors
designed for light lens xerographic applications that are typically coated
on substrates with smooth "mirror" like surfaces where R.sub.max is much
less than 0.4 micron and that do not require an addition of a resin as a
thickening agent in the undercoat layer. This results in a more efficient
operation for equipment changeovers, solution preparation, etc. in the
manufacturing environment. Second, the thin undercoat layer in the
thickness range 0.05-0.5 micron comprising any suitable hydrolyzable
organozirconium, organotitanium or organoaluminum compound with a silane
such as a mixture of acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane, without the addition of a resin
component, produces less residual voltage build up and better cyclic
stability than a thicker undercoat layer comprising the same materials as
above but with a resin component that is added to increase the layer
thickness to provide complete undercoat layer coverage of the substrate in
the event where the surface morphology of the substrate requires a
thickening agent for complete coverage. Currently the liquid honed surface
of the substrate is not optimal for enabling the use of thin undercoat
film materials such as the hydrolyzable organozirconium, organotitanium or
organoaluminum compound with a silane without the addition of a viscosity
increasing agent, which also requires a subsequent humidification
processing step.
COMPARATIVE EXAMPLES
The material package described in the following paragraphs was used to dip
coat a three-layer photoreceptor which has high photosensitivity in the
infrared wavelength region particularly between 700-800 nm. The printers
in which the photoreceptor was tested had an exposure light source at
approximately 780 nm wavelength. The material package described below was
coated on substrates that were specially diamond lathed according to the
present invention (Example 6), diamond lathed to a "mirror" like surface
(Examples 1 and 2), or diamond lathed to a "mirror" like surface and
subsequently liquid honed using a conventional dip coating method
(Examples 3-5).
The substrate employed in all of Examples 1-4 and 6 was 6063 alloy aluminum
which was formed to have either the roughened surface morphology described
in the present invention or surface characteristics with roughness values
outside of the ranges of the present invention. The thickness of the
substrate was approximately 1 mm. For the "mirror" like surface (Examples
1 and 2), which is formed to be as smooth as possible, R.sub.a was less
than 0.05 .mu.m, R.sub.t1(0.1) was less than 50 counts, R.sub.ZISO was
less than 0.3 .mu.m, R.sub.k was less than 0.15 .mu.m, D.sub.a was less
than 0.04 .mu.m and R.sub.max was below 0.4 .mu.m. In the case in which
liquid honing was applied after diamond lathing, a conventional wet honing
method with glass beads was used. After the honing step, the substrate
surface roughness values for Examples 3 and 4 were as follows: R.sub.a
between 0.4-1.0 .mu.m, R.sub.ZISO between 3.4-6.0 .mu.m, R.sub.k between
1.3-3.8 .mu.m, R.sub.max between 5 and 8 .mu.m and D.sub.a between 0.15
and 0.18 .mu.m. After the honing, a cleaning step removed any residual
honing beads prior to dip coating an undercoat layer, a charge generating
layer and a charge transport layer. As part of the class of devices with
honed substrate surface morphology belonging to Example 4, other examples
of honed substrate surface roughness were also examined for pepper spot
evaluation. For example, a three-layer photoreceptor comprising a honed
surface with R.sub.a between 0.15-0.2 .mu.m, R.sub.ZISO between 1.2-1.5
.mu.m, R.sub.k between 0.4-0.6 .mu.m, R.sub.max between 1.8-2.2 .mu.m and
D.sub.a between 0.1 and 0.15 .mu.m was evaluated for pepper spots.
Substrate surface roughness values for Example 5 also belong to this
latter category. The undercoat film used in Examples 1, 4 and 6 included
13 wt % acetylacetone zirconium tributoxide, Orgatics ZC540 available from
Matsumoto Kosho Co. Ltd., and 1.4 wt %
.gamma.-aminopropyltrimethoxysilane, A1110 available from Nihon Unica Co.
Ltd., in 56.4 wt % isopropyl alcohol 28.2 wt % butanol and 1 wt %
deionized water mixture. Example 5 is a typical three-layer photoreceptor
that contains the same materials as examples 1, 4 and 6 in the undercoat
layer but with an addition of a polyvinyl butyral resin, S-Lec BM-1.SP
available from Sekisui Chemical Co., Ltd. as a thickening agent; this
three-component undercoat material requires a humidification processing
step. Examples 2 and 3 had an undercoat film that included a 9 wt % type-8
nylon resin, e.g., Luckamide 5003, available from Dainippon Ink &
Chemicals, Ltd. in a 50 wt % methanol, 33 wt % butanol and 8 wt %
deionized water mixture.
As an example, the charge generating layer for Examples 1-4 and 6 included
a mixture of 1 wt % oxytitanium phthalocyanine (TiOPC) IV and 5 wt %
chloroindium phthalocyanine (ClInPc) in a 4 wt % polyvinyl butyral resin
binder, BUTVAR B-79 available from Monsanto Chemical company, and 90 wt %
n-butyl acetate as a solvent. Example 5 device is a typical three-layer
photoreceptor with metal-free phthalocyanine in a polyvinyl butyral resin
binder as a charge generating layer.
The charge transport layer for Examples 1-4 and 6 included a mixture of 7
wt % tri-p-tolylamine, TTA available from Eastman Kodak company, and 4 wt
% N,N'-diphenyl-N,N'-bis (3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine in
a 14 wt % polycarbonate resin binder, IUPILON Z-200 available from
Mitsubishi Gas Chemical Company, Inc., and 75 wt % monochlorobenzene as a
solvent. Example 5 device contains N,N'-diphenyl-N,N'-bis
(3-methylpheny)-1,1'-biphenyl-4,4'-diamine in a polycarbonate resin binder
as a charge transport layer.
The approximate dried coated layer thickness ranges for the undercoat film
were 0.1-0.2 .mu.m for acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane (Example 6), and 1-2 .mu.m for type-8
nylon (Examples 2 and 3). The typical dried coated thickness for the
undercoat layer of the device of Example 5 is 0.5-2 .mu.m for
acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane and a polyvinyl butyral resin. Dip
coating velocities were determined to achieve appropriate target coating
thicknesses. Typically, faster dip coating velocity results in thicker
layer thicknesses for a given viscosity of a solution. For example, the
coating velocity for the acetylacetone zirconium tributoxide and
.gamma.-aminopropyltrimethoxysilane at a target thickness of 0.1 .mu.m was
175 mm/minute, and the coated layer was dried at 150 degrees C. for 7.5
minutes. The coating velocity for the type-8 nylon was approximately 200
mm/minute for the target thickness of 1.5 .mu.m, and the coated layer was
dried at 145 degrees C. for 10 minutes. The thickness for the dried charge
generating layer film was 0.2-0.3 .mu.m and, for the dried charge
transport layer film, the thickness was 16-18 .mu.m. The coating velocity
for the charge generating layer was approximately 200 mm / minute for the
target layer thickness of approximately 0.2-0.3 .mu.m, and the coated
layer was dried at 106 degrees C. for 10 minutes. The coating velocity for
the charge transport layer was, for example, approximately 85 mm/minute
for 16.5 .mu.m target layer thickness, and the coated layer was dried at
118 degrees C. for 45 minutes.
Table 1 summarizes the results of initial print tests of "pepper spot" and
interference-fringe defect levels. Pepper spot levels were evaluated on
prints using a scale from 0 to 5. A pepper spot level of "0" is required
to meet the acceptable level of print quality established for most
printers and like machine applications.
Interference-fringe defect level was evaluated on prints using a scale from
0 to 3 and above. "0" interference-fringe level is required to meet the
acceptable level of print quality established for most printer
applications and like machines. For both "pepper spot" and
interference-fringe defect analysis, Standard Image References (S.I.R.)
were used for evaluation. Testing conditions for print testing for pepper
spot evaluations in a stringent `A` zone environmental condition were 80%
relative humidity (RH) and 80 degrees F. temperature. Stress tests were
also performed under a `C` zone condition, of which the conditions were
20% RH/60 degrees F., to assess long-term cyclic stability.
As can be seen from Table 1, Examples 1 and 2 display unacceptable levels
of the interference-fringe defect. While Examples 3 and 4 show 0 level of
the interference-fringe defect, unacceptable "pepper spot" levels were
observed. Finally, while Example 5 has acceptable interference-fringe
defect and "pepper spot" performance, the undercoat layer (acetylacetone
zirconium tributoxide and .gamma.-aminopropyltrimethoxysilane) requires
the addition of a thickening agent (polyvinylbutyral resin) and a
humidification processing step. Example 6 (the present invention)
displayed excellent interference-fringe and "pepper spot" performance
without the use of a thickening agent or a humidification processing step.
TABLE 1
______________________________________
Inter-
Pepper ference-
Spot fringe
Substrate/Undercoat
S.I.R.** defect
Example layer level S.I.R. level
______________________________________
Example 1
Mirror lathed/acetylacetone
0 >3
zirconium tributoxide and .gamma.-
aminopropyltrimethoxysilane
Example 2
Mirror lathed/Type-8 nylon
1.5 >3
resin
Example 3
Honed/ 2.0 0
Type-8 nylon resin
Example 4
Honed/acetylacetone
1.0-4.0 0
zirconium tributoxide and .gamma.-
aminopropyltrimethoxysilane
Example 5*
Honed/acetylacetone
0 0
zirconium tributoxide and .gamma.-
aminopropyltrimethoxysilane
with a polyvinyl butyral
resin
Example 6
Special lathed/acetylacetone
0 0
zirconium tributoxide and .gamma.-
aminopropyltrimethoxysilane
______________________________________
*Requires a processing step in a humidification chamber.
**Standard Image Reference (S.I.R.)
Table 2 shows long-term cyclic stability of the present invention
photoreceptor. Even after 10,000 prints, no apparent print degradation was
observed in either the `A` or `C` zones. V.sub.high and V.sub.low,
corresponding to the initial surface potential and the surface potential
at approximately 7 ergs exposure energy, respectively, varied little after
10,000 prints in both zones. In particular, there were no pepper spots or
interference-fringe print defects observed in either the `A` or `C` zones
during the print testing up to 10,000 prints. The testing device was a
Compaq Pagemarq 20 laser printer with 20 pages per minute printing speed,
11 micron toner size and a 780 nm laser diode as the exposure light
source.
TABLE 2
______________________________________
V.sub.low
Number of (approxi-
prints/ V.sub.high
mately 7
Pepper Spot
Device Test Zone (0 ergs) ergs) S.I.R. level
______________________________________
Example 6
initial print/A
340 50 0
Example 6
initial print/C
350 55 0
Example 6
10,000/C 335 50 0
Example 6
10,000/A 320 40 0
______________________________________
Table 3 shows that the voltage characteristics of the present invention has
acceptable performance levels in other respects. Advantages were observed
with regard to electrical characteristics in addition to "pepper spot" and
interference-fringe defect improvement. Acetylacetone zirconium
tributoxide and .gamma.-aminopropyltrimethoxysilane devices showed lower
dark decay, which is a measure of the surface potential drop in the
photoreceptor without any exposure to light, and lower charge depletion
per unit area, which is a measure of the same phenomenon specifically
underneath the scorotron in terms of excess surface charge needed over the
capacitive charge for a certain desired voltage, compared to type 8 nylon
resin devices when measured in a specialized electrical scanner. The
scanner simulates xerographic machine charging and exposure without toner
development and paper transfer processes. The photoreceptor was exposed at
0.28 seconds after scorotron charging to -380 V and voltages were measured
at 0.42 seconds after scorotron charging. Table 3 shows the electrical
measurement results and emphasizes the superiority of the present
invention (Example 6) over, for example, the device described in Example
3, with respect to dark decay and charge depletion per unit area, Q/A.
TABLE 3
______________________________________
Substrate
Under V.sub.dark
Q/A
coat V.sub.high
V.sub.low
decay depletion
Device layer (0 ergs) (7 ergs)
(0.26sec)
(nC/cm.sup.2)
______________________________________
Example 3
Honed/ 358 79 21 8.4
type-8
nylon
resin
Example 6
Special 372 67 15 3.0
lathed/
acety-
lacetone
zir-
conium
tributox-
ide and
.gamma.-
amino-
propyltri
methoxy-
silane
______________________________________
The invention has been described in detail with reference to preferred
embodiments thereof, which are intended to be illustrative, not limiting.
Various changes may be made and may be apparent to those of ordinary skill
in the art without departing from the spirit and scope of the invention as
defined in the following claims.
Top